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Biomedical subjects

B F Overholt

Publications and source records attributed to B F Overholt.

10 recordsLinked to original sources
PubMed1992

Centering balloon to improve esophageal photodynamic therapy.

A cylindrical balloon was developed to improve delivery of circumferential light for photodynamic therapy (PDT) of esophageal carcinoma. The balloon consisted of a 36-mm-long clear cylindrical membrane and a central tube to hold a cylindrical diffuser in the center of the lumen. Three isotropic probes were placed on the outside of the balloon to allow measurement of delivered light dose to the esophageal mucosa. The balloon was tested in the normal esophagus of 8 dogs that were injected with 4.0 mg/kg of PHOTOFRINR. Endoscopy was performed 48 hours following the injection, and under endoscopic observation the balloon assembly was passed, fixed in place, and inflated. A 1-cm cylindrical diffuser was passed into the central tube and 150, 300, and 600 Joules/cm of 630 nm laser light was delivered at 25 cm, 15 cm, and 5 cm proximal to the gastroesophageal junction. One control dog was illuminated using the cylindrical diffuser alone at doses of 300 and 600 Joules/cm of diffuser. Complete circumferential tissue response was obtained when the balloon was used. Relatively uniform light intensities were measured around the lumen. In contrast, noncircumferential and unpredictable PDT responses were generated when the cylindrical diffuser was used without the balloon.

Animals↗
PubMed1992

Comparative pharmacokinetics of the photosensitizer tin-etiopurpurin in dogs and rats.

Photodynamic therapy is a promising new treatment for local eradication of cancer. Little work has been done to define the pharmacokinetics of photodynamic drugs or the variability in drug disposition that may occur between different species and pathophysiological states of tissues. Pharmacokinetic studies of tin-etiopurpurin (SnET2), a lipophilic photosensitizer, were conducted on six Beagle dogs and six Sprague-Dawley rats. Blood was collected up to 24 h following drug administration for measurement of tin-etiopurpurin concentration. Dogs and rats were euthanatized 24 h post-administration and tissues were collected for drug analyses. The plasma drug concentrations were best described by a 2-compartment model (Ct = Ae-alpha t + Be-beta t). Median distribution and elimination half-lives were 0.24 and 0.34 h and 10.21 and 5.25 h for dogs and rats, respectively. The apparent volumes of distribution were 4.26 +/- 1.75 L/kg for dogs and 1.84 +/- 0.36 L/kg for rats. Systemic clearance was 7.56 +/- 2.45 ml/kg/min and 6.63 +/- 0.91 ml/kg/min for dogs and rats, respectively. Drug was detected in all tissues analyzed 24 h after drug administration. Drug was detected only sporadically in skin and muscle and was generally below the limit of detection of the assay. Where comparisons could be made, concentrations of SnET2 were significantly greater in all tissues except jejunum of rats compared to dogs 24 h after drug administration.

Animals↗
PubMed1991

Nd:YAG laser-induced hyperthermia treatment of spontaneously occurring veterinary head and neck tumors.

Conventional hyperthermia treatment of superficial tumors in the oral cavity is troublesome due to difficulty in accessing the lesion. A new hyperthermia technique employing near-infrared radiation delivered through a flexible silica optical fiber is described. The system consisted of an Nd:YAG laser for tissue heating, a He-Ne laser for aiming beam, a computer-controlled optical shutter, an interstitial thermometer, computer, and a printer. A 3-m-long 600-microns silica fiber delivered laser energy to the tumor via surface illumination. Using the aiming beam, the spot size was adjusted to include 5 mm of surrounding normal tissue. A thermocouple implanted in the tumor base provided temperature feedback to maintain desired hyperthermic temperature within the lesion. Three spontaneously occurring canine (two squamous cell carcinomas on the gum, one pigmented melanoma on the hard palate) and one feline tumor (squamous cell carcinoma on the nose) have been treated with Nd:YAG laser hyperthermia. Hyperthermia was delivered at 43.5 degrees C for 1 h. All animals received standard radiation treatment prior to hyperthermia. Nd:YAG laser hyperthermia allowed effective and efficient delivery of heat to veterinary nasal and oral lesions otherwise not treatable with conventional heating techniques.

Aluminum Silicates↗
PubMed1991

Nd:YAG laser hyperthermia treatment of rat mammary adenocarcinoma in conjunction with surface cooling.

Electromagnetic radiation ranging from radiofrequency to microwave has classically been used to induce hyperthermia for treatment of cancer. This paper presents a new technique using near infrared radiation from an Nd:YAG laser in conjunction with surface cooling to induce hyperthermia in a rat tumor model. A CW Nd:YAG laser hyperthermia system was used to induce hyperthermic temperatures in chemically (DMBA) induced rat mammary adenocarcinomas. The laser was interfaced to a computer and a thermometry unit that provided feedback to control the tumor temperature between 43.2-43.5 degrees C. A thermocouple was placed at the base of the tumor and its temperature was used to control laser exposure. All tumors were 10 to 20 mm in diameter. Surface cooling methods investigated included forced air flow from a fan, forced oxygen flow plus an IV drip, and forced moist oxygen flow from a nebulizer. Twelve rat mammary adenocarcinomas have been treated with Nd:YAG laser hyperthermia. In 4 treatments, no surface cooling was employed. In one treatment the surface was cooled using oxygen flow plus IV drip. In 7 treatments the skin was cooled using the nebulizer technique. The nebulization provided the most effective and reproducible surface cooling. Nd:YAG laser hyperthermia delivered in conjunction with nebulizer surface cooling produced efficient heating of rat mammary adenocarcinomas. A mean temperature of 42.1 degrees C was obtained at the base of the tumors while the mean surface temperature was 37.0 degrees C.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Colonoscopic polypectomy: silent perforation.

The management of colon polyps has been completely revolutionized since the introduction of colonoscopic polypectomy. The reductions in patient time, cost, morbidity, and mortality are major advantages. Reported complications include primarily hemorrhage (1.7%) and frank clinical perforation (0.32%). This report describes a silent perforation after the removal of a broad based polyp through the colonscope.

Colon↗
PubMed1975

Colonoscopy. A review.

The technique of colonoscopy has introduced an exciting new modality for the diagnosis and treatment of diseases of the colon. It is not a panacrea, for, as with any technique, limitations are always present; but it offers the single most far reaching advance for the diagnosis and treatment of diseases of the colon that has been offered in the last decade. The next 10 years should indeed prove exciting.

Biopsy↗
PubMedDate not supplied

Laser and photodynamic therapy of esophageal cancer.

With proper selection of patients with non-operative esophageal cancer, palliative therapy with Nd:YAG laser enhances the quality of life by improving the patient's ability to swallow soft or solid food. Also, the use of non-thermal laser light to initiate the process of photodynamic therapy (PDT) is an additional laser technique that appears effective, not just in palliative treatment, but also in the cure of early esophageal cancer. For PDT, considerable work will be necessary to provide standard techniques in tumor staging, light and drug delivery and in light dosimetry. Ultimately, palliative and curative therapy of esophageal cancer will most likely incorporate multiple modalities, including surgery, radiation, chemotherapy, stents, laser and other thermal modalities, photodynamic therapy, and combinations of these methods.

Antineoplastic Agents↗
PubMedDate not supplied

Colonoscopy.

Explore the source record for details and available documents.

Colitis, Ulcerative↗